Caller ID is a service provided by a telephone service provider that provides a user with information regarding an incoming call. Typically, a display associated with a user's telephone, either integrated into the telephone or as part of an adjunct box coupled to the telephone, will display the telephone number and/or name associated with an incoming call. In Type I Caller ID, which occurs when the user's telephone is in an on-hook state (i.e., the user is not already engaged in a telephone call while the incoming call is arriving), the Caller ID data is provided by a central office of the service provider as frequency shift keying (FSK) data between the first and second rings. The user, after the first ring, can thus look at the display to decide, based on the displayed information, whether to answer an incoming telephone call.
In Type II Caller ID, also known as Caller ID with Call Waiting (CID/CW), the user's telephone is in an off-hook state (i.e., already engaged in a telephone call while the incoming call is arriving). In addition to the familiar audible tone, known as a Subscriber Alert Signal ("SAS tone"), that alerts a user to an incoming call waiting telephone call, the central office provides a Caller ID Alert Signal ("CAS tone") to inform the user's telephone equipment that Caller ID data is about to be transmitted, pending receipt of an acknowledgment from the user's telephone equipment. Based on the CAS tone, the user's telephone briefly mutes its transducers (i.e., microphone and speaker) so that the FSK data is not heard by the user or corrupted by the user's speech. The muting period is sufficiently brief that it does not appreciably disrupt the voice communication between the parties to the conversation. The user, after hearing the SAS tone, can then view the display to determine whether to flash-hook over to the incoming call and temporarily place the existing call into a hold status. The flash-hook operation is accomplished by briefly pressing or activating a switch-hook button, which is normally in a first position, such as down, when the telephone is on-hook, and in a second position, such as up, when the telephone is off-hook, to alert the central office to the desire to switch to the incoming call.
When a telephone is equipped to receive Type II Caller ID data, a user who elects to flash-hook to an incoming call, based, for example, on viewing the Caller ID data associated with the incoming call, may subsequently decide to switch back to the original call and temporarily place the newer call in a hold status, and can do so by again activating the switch-hook. The user can switch back and forth between the two calls as often as desired. However, activation of the switch-hook does not automatically result in a flash-hook operation. Frequently, the flash-hook operation does not occur, and the user thus must verbally confirm the identity of the distant party when switching between calls. There is a need, therefore, for a device and process for automatically providing the user with the identity of the presently-connected caller.